251 



Beak very small, depressed to aud hardly projcctinji; beyond the hinge area, 

 which is narrow, linear, and apparently as long as the hinge line. Median .sep- 

 tiHU iu the interior very small and short, about one-fourth the length of the 

 valve. Associated with one of the interior moulds, is the impression of a single 

 spine, which is nearly two-thirds as long as the valve, very slender, and about 

 the same size throughout the part preserved. 



Dorsal valve imperfectly known. In the collection from Erere is a single 

 interior mould of the dorsal valve of a Chonetes, that appears to belong to this 

 species. It is slightly concave, but the margins are broken away. The cardi- 

 nal process is only sufficiently preserved to show that it is divided through 

 the middle, and extends inwards and slightly backwards. The median septum 

 is faintly indicated, as are also the backward extensions of the vascular impres- 

 sions near to it on each side. The muscular impressions are not preserved. 



There is the exterior mould of the dorsal valve of another and a much larger 

 specimen, which probably also belongs to this same species. It measures 38 

 m. m. in breadth by about 21 m. m.in length, and is proportionately more con- 

 vex than the other specimens, but the outline appears to be the same. The 

 surface markings are not preserved. The impression of the hinge area of the 

 ventral valve lies behind it, showing, that, when the specimen was imbedded, 

 the two valves were joined together. At the fissure, which is small and trian- 

 gular, the area is 2 m. m. broad, but it narrows gradually towards the cardinal 

 angles. It lies nearly in the same plane as the margins of the dorsal valve. 



The test is marked with very fine raised lines, which are low and rounded, 

 but, from their imperfect preservation, the manner in which they increase in- 

 number can not be determined. There are about fifteen of the lines within a 

 space of 5 m. m. near the front. 



Two ventral valves measure as follows: length 17 m. m., breadth 2G m. m., 

 depth nearly 3 m. m.; aud 12 m. m , 21 m. m. aud about 2 m. m. 



This is a pretty sjoecies, resembling much Chonetes coronata, 

 Con. Hamilton group, New York and AVestern States ; but it differs 

 from that species in having longer spines, not extending so ob- 

 liquely backward. 



Moderately abundant in the Devonian sandstone of Ercre, asso- 

 ciated with Strejdorhijnchus Agassizii,Vitulina jjustulosa, etc. 



[Named in honor of Prof. T. B. Comstock, photogTaphcr to tlie 

 Morgan Expedition in 1870.-0. F. II.] 



Chonetes Herbert-Smitliii, Hartt, sp. nov., Plate X, figs. 39-42 and 44-47. 



Test small, concavo-convex, transverse, semi-oval or broadly semi-elliptical 

 in outline. Widtli greatest at the hinge line, aud equal to about one and one- 

 third the length. Cardinal extremities forming nearly right angles ; the 



